RELATED ART
As materials for thermistors which may be employed at higher temperatures, there have so far been employed (a) a material composed mainly of compounds of a corundum type crystal structure, as disclosed for example in JP Patent KOKAI Publication No. 50-118294 (JP-A-118294/75) or "Fine Ceramics Handbook" by Kenya HAMANO, published by ASAKURA SHOTEN in 1984, (b) a material composed mainly of compounds of a spinel type crystal structure, as disclosed for example in JP Patent KOKAI Publication No. 49-63995 (JP-A-63995/74), (c) a material composed mainly of ZrO.sub.2, as disclosed in "Internal Combustion Engine" vol. 30, number 8, page 98, and (d) a material mainly composed of compounds of a perovskite type crystal structure.